It is well established that chronic inflammation contributes to cancer development. Many studies have demonstrated that inflammatory leukocytes promote epithelial cancer by providing soluble growth and survival factors to initiated cells and contribute to tissue remodeling and angiogenesis via synthesis of extracellular proteases; thus, physiological processes necessary for tumor development (enhanced cell survival, tissue remodeling and angiogenesis) are regulated, in part, by leukocytes and the soluble mediators they deliver. However, molecular mechanisms mediating the dialogue between infiltrating immune cells with initiated epithelia are poorly characterized. Moreover, the degree to which these interactions alter stem cell niches in neoplastic environments have not been explored. We hypothesize that infiltrating immune cells regulate niche autonomy of putative lung cancer stem cells through activation of Wnt and Sonic hedgehog (Shh) signaling cascades in initiated lung epithelia; thus, the goals of this project are to define the lineages of functionally significant immune cells that potentiate cancer development in lung, determine which of these regulate Wnt and Shh signaling in lung epithelia, and determine if in so doing, they confer stem cell niche autonomy to initiated epithelial cells and therefore enhance tumorigenic potential. To assess our hypothesis, we propose to, 1) define the profile of immune cells associated with human and mouse lung carcinogenesis and determine how these correlate with presence of CD133+ cells and activation of Wnt and Shh signaling cascades, 2) define functional significance of recruited immune cells as regulators of Wnt and Shh signaling during lung carcinogenesis, and 3) Define the functional significance of immune cells as regulators of Wnt and Shh signaling and their combined effects on putative lung cancer stem cells.